A commercially-available ultra low-cost laser rangefinder is finally set to hit department store shelves in February! I'm speaking of the laser rangefinder presented at ICRA 2008 that costs $30 to build (commented on here at Hizook almost one year ago) that sits atop the recently announced Neato Robotics XV-11 vacuum cleaner. Others have thoroughly discussed the XV-11's competitiveness with iRobot products, the possible patent infringement of iRobots square-front design, and its ability to perform SLAM (Simultaneous Localization and Mapping). But everyone has glossed over the coolest part: Forget about Neato's $400 robot, $60 batteries, $30 wheels (etc.)... if made available, sub-$100 laser rangefinders would revolutionize hobby robotics! Read on for a description of this compelling (future?) component.
Neato sponsored an ICRA 2008 research paper entitled, "A Low-Cost Laser Distance Sensor," that detailed the design of laser rangefinder that costs only $30 to build. Called the "Revo LDS", it is pictured below.
Unlike the more expensive (many thousands of dollars) laser rangefinders that use time of flight measurements, such as those discussed here and here, the Revo LDS triangulates the distance to an object using a fixed-angle laser pointer and a CMOS imager, with a known baseline between the two. To quote:
A compact, rigid point-beam triangulation module incorporating laser, imager, and electronics. With a low-cost CMOS imager and a DSP for subpixel interpolation, we get good range resolution out to 6 m with a 5 cm baseline, at a 4 KHz rate. The key insight to the Revo is that high precision is possible with a small baseline, because of the digital image sensor.
A motor spins the unit at 10Hz to give a full 360-degree field of view. An optical encoder gives 1-degree angular accuracy. Not exactly Earth-shattering, but simple and low-cost. An enclosed, robust USB version of this sensor would have broad appeal, and open up the world of hobby robotics to a sensor that is ubiquitous on research robots. Oh, and I suppose the XV-11 isn't half-bad either:
I seriously hope that Neato makes the laser rangefinder component available separately, but rumor has it that they have no intention to do so. At the moment, I am a bit worried about the possibility of litigation due to similarities between the XV-11 and an iRobot patent (see below). Hopefully they see the light and avoid destructive lawsuits.
While I'm on the topic... The idea of triangulating distances using lasers and cheap CMOS/CCD imagers is by no means new. My favorite example is Morgan Quigley's "Borg Scanner" from Stanford's STAIR Lab. The Borg Scanner performs triangulation along an entire line (plane) simultaneously using the exact same technique. Scanning a green laser-line across a scene produces dense 3D point clouds. You can see a few photos and a video of it being used below. A forthcoming ICRA 2009 paper on the scanner entitled "High-Accuracy 3D Sensing for Mobile Manipulation: Improving Object Detection and Door Opening" is also quite good. I've heard rumors that design and fabrication details for this sensor is going to be released as "open source"; I am anxious to give it a try.
Whether a commercial unit or home-brewed open source initiative, it appears that ultra low-cost laser rangefinders are on the horizon. Next on the wish-list: low-cost flash LADAR -- perhaps Microsoft's Project Natal will deliver...?